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From: reaper@wixer.helps.cs.utexas.edu (Keath Milligan)
Newsgroups: comp.os.msdos.programmer
Subject: Re: HD park
Message-ID: <1991May22.170907.2417@wixer.helps.cs.utexas.edu>
Date: 22 May 91 17:09:07 GMT
References: <29586@hydra.gatech.EDU>
Organization: Real/Time Communications
Lines: 49

As far as I know, there is no standard sub-function 19 (or 19h) to the BIOS
diskette services interrupt 13h.

My version of PARK.COM parks the hard-drive heads by first using interrupt 13h,
sub-function 08h (with the fixed-disk drve number in DL, 80h for the first
fixed-disk, 81h for the second and so forth) to return the parameters for the
drive:

		mov ah,08h
		mov dl,80h
		int 13h
		jc  error	;your error-handler, error code in ah
		cmp dl,0	;dl=0 == no fixed disks attached
		je  error_nod	;another error-handler you should write

Int 13h, function 08h will return the number of tracks per side in CH, the
number of sectores per track in CL, number of sides (heads) in DH, number of
consecutive drives attached in DL, a pointer to a parameter-table in ES:DI,
and, finally, if the drive is a floppy, a drive type value in BL.  For the most
part, you only need to be concerned about the number of sides (DH) and the
number of tracks per side (CH) in order to park the heads.

Next, function 11h (recallibrate fixed disk) of Int 13h is used:

		mov ah,11h
		mov dl,80h
		int 13h
		jc error

I can't seem to find much documentation on this function, so I'm afraid I don't
know exactly what it does... 

Finally, function 0Ch (seek cylinder) is used once to seek track 0 and then
again to seek the maximum track# for a side:

		mov ah,0Ch
		mov cx,0	;seeking track 0, sector 0
		mov dl,80h	;fixed-disk #
		mov dh,0	;head number
		int 13h		;seek track 0

		mov ah,8   	;get drive parameters
		mov dl,80h	;fixed-disk #
		int 13h		;get max tracks per side in ch

		mov ah,0Ch
		mov dl,80h
		mov dh,0	;head#
		int 13h		;seek track in ch